1. Field of the Invention
The present invention relates to a drive mechanism with an ultrasonic motor, and to an electronic device using the drive mechanism with the ultrasonic motor.
2. Description of the Related Art
Generally, optical apparatuses have an aperture or shutter mechanism for controlling the quantity of introduced light. Such an aperture mechanism is designed to control the quantity of introduced light by moving aperture blades which cover the aperture. To drive the blades, an electromagnetic actuator or a stepping motor is ordinarily used in combination with any of various motive power transmission mechanisms using toothed wheels, etc.
Conventionally, from an output shaft attached to the rotor of such an electromagnetic actuator or a stepping motor with little driving force, motive power is transmitted through a complicated power transmission mechanism. The conventional drive mechanisms for the above-mentioned purpose are large in size and have low positioning resolution. With respect to shutters, there is a limit to the shutter opening/closing speed. In the case of an aperture mechanism or the like, there is a need to keep a current running for maintaining the mechanism stopped in a certain position. In particular, there is a problem of fast exhaustion of batteries in portable devices such as cameras and video camera-recorders relating to such a need.
Further, the conventional electromagnetic actuators or motors are liable to generate electromagnetic noise such as to seriously affect communication and medical apparatuses. Conversely, they are caused to malfunction in the presence of magnetic fields.
In view of the above-described circumstances, an object of the present invention is to provide a drive mechanism using an ultrasonic motor for directly driving a driven member without a transmission mechanism using toothed wheels or the like.
To achieve the above-described object, the present invention employs, an ultrasonic motor as an actuator which is small in size and thickness, having a large torque, a stationary torque and has improved response, and is insensitive to magnetism, and provides a drive mechanism with an ultrasonic motor comprising an ultrasonic motor having a vibrating member including a piezoelectric element, and a rotor capable of rotating by receiving vibration of the vibrating member, at least one driven member linked to the rotor and driven by being linked to a rotary motion of the rotor, a guide member for restricting the rotation of the driven member to guide the driven member in a direction in which the driven member is to be driven.
The rotor of the ultrasonic motor is in the form of a plate because of the essential qualities of the ultrasonic motor. Therefore, the driven member can be rotatably attached to portions of the rotor other than the rotary shaft.
In this aspect of the present invention, a guide member is provided on the outside of the rotor to movably guide the driven member so that the driven member does not rotates with the rotation of the rotor, thereby enabling the moving member to move separately from the rotary motion of the rotor.
According to the present invention, therefore, it is possible to provide a drive mechanism which uses an ultrasonic motor to directly drive a driven member without a transmission mechanism using toothed wheels or the like, which is small in size, and which has high positioning accuracy.
The rotor may be directly pressed against the piezoelectric element or may be pressed against the piezoelectric element with a vibrating member interposed therebetween, the vibrating member amplifying elliptical vibration caused by expanding vibration of the piezoelectric element.
According to the present invention, the above-described drive mechanism with the ultrasonic motor may comprise the projecting portion (e.g., rotation range limiting member 15b) provided on the rotor, and a receiving member (e.g., spring seat 16a) for limiting the range of rotation of the rotor and limiting the range of movement of the driven member by receiving the projecting portion coming to the receiving member by a turning movement.
In this case, since the range of rotation of the rotor is limited, the moving member is inhibited from moving so as to exceed allowable limits, so that reliability of the drive mechanism with the ultrasonic motor can be improved.
More specifically, according to the present invention, there are provided a pressing spring (e.g., a plate spring 16) for pressing at least one of the rotor and the piezoelectric element against the other so that the pressure for contact therebetween is increased, and a spring seat (16a) for holding the pressing spring. This spring seat is constructed to also function as a receiving member.
Specifically, the driven member is linked to the rotor through the projecting portion.
In the above-described drive mechanism with the ultrasonic motor, a cushioning material for absorbing a shock may be provided between the projecting portion and the receiving member, thereby reducing the possibility of such a shock at the time of receiving seriously affecting the device incorporating the drive mechanism with the ultrasonic motor.
According to the present invention, in the above-described drive mechanism (1) with the ultrasonic motor, the driving direction in which the driven member is guided by the guide member (19b) is a rectilinear direction.
According to the present invention, it is possible to provide a drive mechanism with an ultrasonic motor capable of directly converting a rotary motion of a rotor into a rectilinear motion of a driven member.
According to the present invention, a plurality of driven members may be driven in different directions to each other. More specifically, separate driven members (e.g., aperture blades 21) are attached to the same rotor at two positions, and are moved in opposite directions to each other.
According to the present invention, it is also possible to obtain a drive mechanism (2) with an ultrasonic motor in which each of two driven members has an aperture (21C), the two driven members are placed in an overlapping manner such that the aperture of one driven member is covered with the other driven member, and the amount of overlap of the two driven members is changed by rotational movement of the rotor to change the amount of opening (21d) of the aperture.
This mechanism can be used as an aperture mechanism for light quantity control or a shutter mechanism.
The present invention also provides a drive mechanism (3) with an ultrasonic motor comprising an ultrasonic motor having a vibrating member including a piezoelectric element, and a rotor capable rotating by receiving vibration of the vibrating member, a rotating member linked to the rotor and rotated by being linked to a rotary motion of the rotor, a driven member linked to the rotating member and driven with the rotation of said rotating member, and an axial member for rotatably supporting said driven member.
According to the present invention in this aspect, the driven member is a lever with the axial member and the rotor operating as a fulcrum and a point of action, respectively. Therefore, it is possible to provide, by utilizing the principle of the lever, a drive mechanism with an ultrasonic motor using a rotary motion of the drive mechanism rotor as a direct motive power source.
According to the present invention, it is also possible to obtain a drive mechanism with an ultrasonic motor comprising an aperture member (e.g., rotary member 31) having an aperture (31a), wherein the driven member is placed so that at least one portion overlaps the aperture of the aperture, and wherein the amount of overlap of the aperture and the driven member is changed with a rotational movement of the rotor to change the amount of opening of the aperture.
This mechanism can be used as an aperture mechanism for light quantity control or a shutter mechanism.
The present invention also provides a drive mechanism with an ultrasonic motor comprising an ultrasonic motor having a vibrating member including a piezoelectric element, and a rotor capable of being rotated by vibration of the vibrating member, a first driven member linked to the rotor and driven by being linked to a rotary motion of the rotor, a rotating member maintained in contact with the rotor and rotated by being linked to the rotary motion of the rotor, a second driven member linked to the rotating member and driven by being linked to the rotary motion of the rotating member, and an axial member for restricting the rotation of each of the first and second driven members and axially supporting the first and second driven members.
According to this aspect of the present invention, the two driven members can be used as hands for pinching and holding an object. Also, free end portions of the first and second driven members project toward each other and overlap with each other to have an overlap portion, and the amount of opening of the aperture (42e) formed by being surrounded by the first driven member and the second driven member is changed by a rotational movement of the rotor.
This mechanism can be further used as an aperture mechanism for light quantity control or a shutter mechanism.
The above-described drive mechanism with the ultrasonic motor may further be constructed to have rotation amount detection means (e.g., slit member 7 and light emitting and receiving device 16b) for detecting the amount of rotation of the rotor, and a control unit (18) for controlling the ultrasonic motor according to the amount detected by the rotation amount detection means.
In this case, since the ultrasonic motor is controlled by detecting the amount of rotation of the rotor, i.e., the amount of driving of the driven member, the drive mechanism with the ultrasonic motor can perform driving with improved accuracy.
This rotation amount detection means is, for example, a method of irradiating light on a slit member provided on the rotor, receiving transmitted light or reflected light obtained in a digital manner, and analyzing the number of pulses thereby obtained.
Further, the drive mechanism with ultrasonic motor may further be constructed to have a light quantity sensor for detecting the quantity of light passing through the aperture, and a control unit for changing the amount of opening of the aperture by controlling the ultrasonic motor according to the amount detected by the light quantity sensor. The amount of movement of the rotor is controlled while directly detecting the control-object light quantity, thus enabling highly accurate light quantity control.
The present invention also provides an electronic device with the ultrasonic motor having the above-described drive mechanism with the ultrasonic motor.
According to the present invention, the drive mechanism with the ultrasonic motor of the present invention is smaller and more accurate in positioning than the conventional drive mechanisms. Therefore, if the drive mechanism of the present invention is used, electronic devices, such as still cameras, video camera-recorders, electronic watches, measuring apparatuses, printers, printing machines, machine tools, robots, transfer apparatuses, and storage units, can be designed so as to reduce the overall size and the accuracy.